The role of the PCA3 assay in predicting prostate biopsy outcome in a South African setting

Abstract:

OBJECTIVES
• To evaluate the investigational role, ideal
threshold and indications of the Prostate
CAncer gene 3 (PCA3) assay in a South
African context.
• To better define the universality of the
above marker since this is the pioneer study
on the continent of Africa.
PATIENTS AND METHODS
• We prospectively evaluated 105
consecutive South African men referred for a
prostate biopsy at two tertiary centres in the capital city, Pretoria.
• Sequentially, PSA levels and post DRE
urine samples were taken within 24 h before
prostate biopsy.
• The urine specimen was tested using the
PROGENSA TM PCA3 assay and a score was
generated as (PCA3 mRNA/PSA mRNA)× 1000.
• The performance of this assay in
predicting biopsy outcome was assessed,
and compared with that of serum PSA.
RESULTS
• Median patient age was 67 years with a
positive biopsy incidence of 42.9%.
• The higher the PCA3 score the greater the
probability of a positive biopsy (
P
=
0.003).
• This score performed independently of
prostatic volume (
P
=
0.3889) or the
presence of a concurrent primary
malignancy (
P
=
0.804).
• A threshold of 60 revealed a positive
predictive value of 60% with an odds ratio of
4, whereas setting a limit of 35 revealed a
positive predictive value of 54% and odds
ratio of 3.5.
• Using receiver operating characteristics
for overall performance comparison, the PSA
level (area under the curve 0.844) performed
better than the PCA3 score (area under the
curve 0.705).
CONCLUSION
• PCA3 assay has shown consistency and
performed in line with previous studies
but it did not surpass serum PSA in this
population.
• A PCA3 assay threshold of 60 performed
better than the conventional limit of 35.
• This assay may have a potential niche in a
certain subset of South African men that
includes patients with larger glands,
previous negative biopsies and altered
baseline PSA levels.